1. Field of the Invention
The invention relates to an arrangement and appertaining method for setting the speed of an intermediate carrier in an electrophotographic printer device.
2. Description of the Related Art
Electrophotographic printer devices are known (for example, U.S. Pat. No. 4,774,524). In these devices, a charge image of the image to be printed is generated on an intermediate carrier (e.g., a photoconductor drum), is transfer-printed onto a recording medium (e.g., paper), and is subsequently fixed on the recording medium.
There are digital electrophotographic printer devices that can process continuous stock with a transport perforation as a recording medium. There are also electrophotographic printer devices that can process recording media without a transport perforation (pinless) with a suitable transport device. Given printing systems with a plurality of successively coupled printer devices (for example, a twin system with two printer devices, or a triple system with three printer devices), the recording medium to be printed may problematically shrink in the longitudinal direction in the first printer device or following printer devices when using thermal fixing. In order to compensate this length change in every following printer device, the transport device for the recording medium in this printer device must run slower by the amount of shrinkage.
Due to the slower running of the recording medium, a relative velocity derives between recording medium and intermediate carrier since the speed of the intermediate carrier in printer device 2 or 3 is not reduced. The print image present on the intermediate carrier and composed of correspondingly arranged toner material can then be smeared at certain locations in the transfer printing event between intermediate carrier and recording medium due to the relative velocity. This appears as disturbing transverse streaking and in raster area of the print images on the recording medium that appear restless.
The invention provides an arrangement for setting the speed of an intermediate carrier that considers changes in the dimensions of the recording medium in longitudinal direction that are present before entry into the printer device.
This problem is solved by an arrangement for setting a speed of an intermediate carrier in an electrophotographic printer device which generates print images that are transfer-printed onto a recording medium moved by a transport mechanism, comprising an intermediate carrier drive configured to adapt a speed of the intermediate carrier to a feed velocity of the transport mechanism in order to compensate for changes in dimensions of the recording medium in a longitudinal direction that are present before entry into the transport mechanism.
This problem is also solved by a method for setting the speed of an intermediate carrier in an electrophotographic printer device, comprising generating print images on the intermediate carrier that are transfer-printed onto a recording medium and moved by a transport mechanism; adapting an intermediate carrier speed to a speed of the recording medium that considers changes in dimensions of the recording medium in a longitudinal direction that occurred before entry into the transport mechanism. This method may also further comprise providing a plurality of electrographic printer devices in sequence; and respectively storing in a table, for each printer device, an intermediate carrier speed (v(z, real)) with a value dependent on a position of a respective printer device in the sequence of printer devices. The invention is explained in more detail below.
The invention is very advantageous when a plurality of printer devices in a printing system print successively on a recording medium. The following description proceeds on the basis of this case. However, the invention could also be utilized in an individual printer device since irregularities in the print image are avoided in any case given a coupling of the speed of the intermediate carrier to that of the recording medium.
Up to now, intermediate carriers in all printer devices of a printing system have been driven with an identical (normal) speed regardless of whether they represent the first, second or some further printer device. As a result, there are sometimes disturbing degradations of the print image in printing systems having a plurality of printer devices. These disadvantages are now prevented by use of the inventive arrangement.
To that end, the speed of the intermediate carrier in the previously mentioned printing systems is adapted to the shrinkage of the recording medium that arises in preceding printer devices in order to achieve an improvement of the transfer printing quality and, thus, an improvement of the print quality on the recording medium. Developments of the invention are described below.
In order to adapt the speed of the intermediate carrier to the shrinkage of the recording medium, a table can be provided in the controller for the intermediate carrier drive in which the speed adapted to the shrinkage of the recording mediumxe2x80x94also called real speedxe2x80x94is stored for the appertaining electrophotographic printer device. A table that contains the adapted (or real) speed for the recording medium feed can also be provided in the controller for the transport device.
The speed of the intermediate carrier can also be adapted to the modified dimensions of the recording medium in that it is coupled to the feed velocity of the recording medium. It is then advantageous when the transport device separately calculates the feed velocity of the recording medium for each electrophotographic printer device. This is possible, for example, when synchronization marks are applied on the recording medium that are respectively sensed by the transport devices of the electrophotographic printer devices, which can enable the adapted or real speed of the recording medium to be determined. The real speed of the intermediate carrier can then be calculated from the real speed of the recording medium.
Given a printing system composed of a plurality of electrophotographic printer devices, it is expedient when the first printer device applies the synchronization marks onto the recording medium.
The intermediate carrier of the electrophotographic printer devices can be photoconductor drums or photoconductor belts.